Weather Service Report


049 
FXUS66 KPQR 261040
AFDPQR

AREA FORECAST DISCUSSION 
NATIONAL WEATHER SERVICE PORTLAND OR 
240 AM PST MON JAN 26 2015

.SYNOPSIS...A STRONG RIDGE OF HIGH PRESSURE ALOFT WILL CONTINUE TO 
MOVE AWAY TO THE E TODAY...WEAKENING THE LOW LEVEL INVERSION LATER 
TODAY. A VERY WEAK FRONTAL SYSTEM WILL APPROACH THE COAST LATE 
TONIGHT...THEN LINGER OVER NW OREGON AND SW WA THROUGH WED. ANOTHER 
RIDGE OF HIGH PRES IS EXPECTED TO DEVELOP OVER THE PACIFIC NW LATE 
IN THE WEEK AND CONTINUE INTO THE WEEKEND. 
&&

.SHORT TERM...SURFACE OBSERVATIONS AND SATELLITE FOG CHANNEL IMAGERY 
INDICATED AN AREA OF WIDESPREAD FOG AND LOW STRATUS EXTENDING FROM 
THE I-5 CORRIDOR IN SW WA S THROUGH THE LOWER COLUMBIA AND 
WILLAMETTE VALLEYS EARLY THIS MORNING. AS WAS SEEN RATHER 
DRASTICALLY IN THE 00Z SLE SOUNDING SUN AFTERNOON...A VERY STRONG 
INVERSION WAS THE CAUSE OF THE FOG TRAPPED IN THE LOWER VALLEYS 
WHILE ABOVE ABOUT 1K FT CONDITIONS WERE MUCH WARMER AND DRIER. WATER 
VAPOR PICTURES EARLY THIS MORNING SHOWED THE UPPER RIDGE WAS STILL 
IN PLACE OVER OREGON FOR CONTINUED STABLE CONDITIONS...BUT MODELS 
ALL EXPECT THE RIDGE AXIS TO MOVE RAPIDLY E TODAY WHICH WILL RESULT 
IN A WEAKENING INVERSION. MANY AREAS WERE STILL REPORTING 
VISIBILITES AT OR BELOW A QUARTER MILE...SO WILL CONTINUE WITH THE 
DENSE FOG ADVISORY THIS MORNING. ALTHOUGH THE INVERSION WEAKENS 
TODAY...IT STILL MAY NOT BE ENOUGH TO BREAK UP THE INLAND STRATUS 
EVERYWHERE SO ANOTHER RELATIVELY COOL DAY CAN BE EXPECTED IN THE 
INTERIOR VALLEYS...WITH WARMER ALTOUGH NOT QUITE SO WARM TEMPS AT 
HIGHER ELEVATIONS. 

WITH THE WEAKENING OF THE INLAND SURFACE HIGH TODAY...MODELS 
GENERALLY AGREE ON A SWITCH TO SSW ONSHORE WINDS ALONG THE COAST 
TODAY. THIS WILL MODERATE TEMPS ON THE COAST TODAY...AND WILL 
ULTIMATELY PUSH SOME MARINE CLOUDS ONTO THE COAST AND SLOWLY SPREAD 
THEM INLAND TONIGHT. AS THE UPPER RIDGE COLLAPSES...A RATHER FLAT 
WESTERLY FLOW DEVELOPS ALOFT TONIGHT AND CONTINUES THROUGH WED. 
MODELS REMAIN IN GOOD AGREEMENT IN SHOWING A DECAYING FRONT SAGGING 
DOWN INTO THE NW PART OF THE FORECAST AREA LATE TONIGHT AND 
LINGERING THROUGH WED. MODEL CROSS SECTIONS INDICATE THERE IS SOME 
DEPTH TO THE MOISTURE OVER THE N COASTAL AREAS WITH THIS BAROCLINIC 
ZONE...WHILE FURTHER TO THE S AND E MOISTURE BECOMES SHALLOWER. WILL 
KEEP CHANCE POPS OVER THE NW PART OF THE AREA FROM LATE TONIGHT 
THROUGH WED...AND TAPER OFF ANY CHANCES FOR LIGHT PRECIPITATION 
FURTHER TO THE S AND E. THE RETURN TO WEAK ONSHORE FLOW WILL BRING 
TEMPS DOWN CLOSER TO SEASONAL NORMALS. 

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS. WEDNESDAY 
NIGHT THROUGH SUNDAY...A PASSING SHORTWAVE LATE WED NIGHT MAY 
PROVIDE ENOUGH LIFT FOR A FEW SHOWERS...MOSTLY ALONG THE NORTH COAST 
AND COAST RANGE AND INTO SW WASHINGTON. MODELS REMAIN IN GOOD 
AGREEMENT THAT A RIDGE OF HIGH PRES ALOFT REBUILDS ON THU AND 
PERSISTS THROUGH THE END OF THE WEEK. THIS WILL MAINTAIN DRY 
CONDITIONS BUT BRING DAILY FOG AND LOW CLOUDS TO INTERIOR VALLEY 
LOCATIONS. THE RIDGE WILL LIKELY BREAK DOWN AND SHIFT INLAND SOME 
TIME NEXT WEEKEND...BUT STILL SOME UNCERTAINTY AS TO IF THIS WILL BE 
SAT OR SUN. THE 12Z GFS IS A BIT MORE AGGRESSIVE IN BRINGING A MOIST 
FRONTAL SYSTEM TO THE REGION BY LATE SAT NIGHT...WHILE THE ECMWF 
WOULD KEEP THINGS DRY UNTIL SUN NIGHT. INCREASED POPS A BIT FOR NEXT 
WEEKEND...PARTICULARLY FOR THE NW PORTION OF THE FORECAST 
AREA...THOUGH RESTRICTED TO LOWER END CHANCE FOR SAT NIGHT THROUGH 
SUN GIVEN THE SUPPORT FOR THE LATER TIMING FROM THE ECMWF AND 
NUMEROUS GEFS MEMBERS. CULLEN
&&

.AVIATION...HIGH PRESSURE AND A STRONG INVERSION HAVE LED TO MOST
TAF SITES DROPPING DOWN INTO LIFR AND IFR CONDITIONS. EXPECT KEUG
AND KSLE TO EXPERIENCE THESE REDUCTIONS THROUGH A GOOD PORTION OF
THE NEXT 24 HOURS. KHIO MAY ALSO FALL INTO THIS CATEGORY.
HOWEVER...EAST WINDS POURING OUT OF THE COLUMBIA RIVER GORGE ARE
CURRENTLY PRODUCING VFR CONDITIONS AT KPDX AND KTTD. THESE EAST
WINDS SHOULD SUBSIDE TODAY...AND IF THE LIFR/IFR FOG DOES NOT
RETURN TO THESE SITES LATER THIS MORNING...EXPECT REDUCTIONS TO
DEVELOP TONIGHT. A SOUTHERLY WIND REVERSAL IS ALSO PUSHING
NORTHWARD OFFSHORE. STRATUS OFF THE COAST SHOULD PUSH ASHORE LATER
TODAY AND TONIGHT...AND BRING IFR CONDITIONS TO KAST AND KONP.
HOWEVER...MODELS ARE STRUGGLING WITH THE CURRENT PLACEMENT OF IT
RIGHT NOW SO UNCERTAINTY IN THE TIMING OF WHEN THESE REDUCTIONS
WILL OCCUR IS HIGH.

KPDX AND APPROACHES...LIGHT EAST WINDS POURING OUT OF THE COLUMBIA
RIVER GORGE CONTINUE TO BRING A MIX OF VFR AND LIFR CONDITIONS TO
THE TERMINAL. EXPECT THE EAST WINDS TO DOMINATE FOR THE NEXT
SEVERAL HOURS...BUT A GRADUAL WEAKENING OF THE HIGH PRESSURE EAST
OF THE CASCADES SHOULD ALLOW IFR CONDITIONS TO RETURN LATER THIS
MORNING. HOWEVER...CONSIDERABLE UNCERTAINTY EXISTS IN THE TIMING
OF WHEN THE SWITCHES FROM VFR TO LIFR/IFR WILL OCCUR. /NEUMAN

&&

.MARINE...A SOUTHERLY WIND SURGE IS CURRENTLY UNDERWAY AND MAY
LEAD TO BRIEF PERIOD THIS MORNING OF WIND GUSTS AROUND 20 KT
ACROSS THE WATERS. OTHERWISE...A WEAK FRONT DROPPING SOUTHEASTWARD
WILL BRING A WIND SHIFT TO THE WATERS ON TUESDAY...BUT HAVE
LITTLE APPRECIABLE IMPACTS TO MARINE INTERESTS. HIGH PRESSURE IS
THEN EXPECTED TO BUILD BACK OVER THE WATERS LATE IN THE WORK WEEK
WITH LIGHT WINDS CONTINUING. SEAS WILL GENERALLY SUBSIDE DURING
THIS TIME...AND END UP WELL BELOW 10 FT. THERE IS A DECENT CHANCE
A MORE ACTIVE STORM PATTERN WILL DEVELOP LATE IN THE WEEKEND AND
NEXT WEEK SO EXPECT SEAS AND WINDS TO INCREASE. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...DENSE FOG ADVISORY UNTIL 11 AM PST THIS MORNING FOR CENTRAL 
     WILLAMETTE VALLEY-GREATER PORTLAND METRO AREA-LOWER 
     COLUMBIA-SOUTH WILLAMETTE VALLEY.

WA...DENSE FOG ADVISORY UNTIL 11 AM PST THIS MORNING FOR GREATER 
     VANCOUVER AREA-I-5 CORRIDOR IN COWLITZ COUNTY.

PZ...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 7 AM
     THIS MORNING TO NOON PST TODAY.
&&

$$

INTERACT WITH US VIA SOCIAL MEDIA     
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND
 
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON 
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS 
COMMONLY REFERRED TO AS THE FORECAST AREA.

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